1. Field of the Invention
The present invention relates to a fastener for lumbosacral osteosynthesis, making it possible to secure and assemble the damaged vertebral stages of this part of the spinal column.
2. History of the Related Art
We know of fasteners of this type which generally include two essentially parallel units, each comprising:
a cylindrical rod whose length is a function of the height and the number of vertebral stages to be joined; PA1 and several units, each composed of a ring, a nut and a pedicle screw used for fastening the rods into the pedicles of each vertebra.
Such fasteners necessitate the alignment of the pedicle screws in the sagittal and frontal plane. Actually, if the alignment is not observed, the joining and connection by the rod is impossible, unless the rod is deformed so as to account for the angular displacement.
Moreover, the known fasteners have risks of a subsequent degeneration of the disc which lies immediately adjacent the assembly of mechanically locked or connected vertebrae. In effect, after the lumbosacral osteosynthesis, the disc receives all stresses which, in a normal state, are distributed to the several stages.
These are the drawbacks that the present invention intends to correct.